Mobile machines, such as marine vessels, often include multiple engines harnessed together to drive one or more primary loads (e.g., propellers) and various auxiliary loads (e.g., HVAC, lighting, pumps, etc.). These engines may have different operating ranges, speeds, etc. The engines can be mechanically connected to the loads or electrically connected to the loads by way of generators. In some applications, the loads of a vessel can be driven both mechanically and electrically in a hybrid arrangement.
In typical marine applications, multiple engines are simultaneously operated to satisfy a power demand. Each of the multiple engines produces a share of the power demand proportional to the engine's capacity. For example, a particular marine vessel may have two engines capable of producing 2,000 kW each, and two engines capable of producing 5,000 kW each. If the total power demand is 7,000 kW, the share of the load distributed to each engine may be 1,000 kW, 1,000 kW, 2,500 kW, and 2,500 kW, respectively. However, such a rigid load-sharing configuration may not be the most fuel efficient one. This is because each engine may have a particular fuel consumption curve nonlinearly dependent on the power produced by the engine. For instance, it may be more fuel efficient to distribute the load such that the engines produce 1,200 kW, 500 kW, 2,300 kW, and 3,000 kW, respectively.
An attempt at improving power generating efficiency is disclosed in Chinese Patent No. 101577425 to Toruya et al. (Toruya) that published on Mar. 27, 2013. Toruya discloses a load distributing system used in a power grid. The power grid has multiple generators sets. The system stores a fuel consumption curve associated with each generator set. For a given power demand, the system uses the fuel consumption curves to compute a load-sharing configuration that leads to a minimum total fuel consumption. The system works only offline and stores the computation results in a table. Later, when the power grid receives a power demand, the system or a human operator can look up the corresponding load-sharing configuration in the table.
Although Toruya offers a way of quantitatively determining a load-sharing configuration among multiple generator sets to reduce the total fuel consumption, it does not adequately consider the differences among the generator sets. For example, generator sets with the same fuel consumption curve may operate under different operating constraints, and therefore have different operating priorities in the load sharing. Sometimes, it may be desired for a lower-priority generator set to participate in the load sharing only after the combined power output produced by all the higher-priority generator sets exceeds a certain threshold. Moreover, Toruya only works offline and may not timely respond to rapid changes of the power demand.
The disclosed system is directed to overcoming one or more of the problems set forth above and/or other problems of the prior art.